• Development of a uniform framework for the integrated specification and verification of constructor-based visible types on the one hand and state-based hidden types on the other hand. We call them swinging types and use them in various application areas, in particular those where - traditionally - modal logic or object-oriented programming plays the major rôle. The semantics of swinging types is given by Herbrand models with least and greatest relational fixpoints. Proofs about swinging types make heavy use of induction and coinduction. (Peter Padawitz)

• The prototyping system Expander2 is a multi-purpose workbench for interactive logical inference, constraint solving, data flow analysis and other rule-based manipulations of algebraic terms, logical formulas and graphical representations thereof, which range from term graphs to various turtle-system-generated pictures Expander2 has been written in O'Haskell, an extension of Haskell with object-oriented features for reactive programming and a typed interface to Tcl/Tk for developing GUIs. Besides a comfortable GUI the design goals of Expander2 were to integrate testing, proving and visualizing deductive methods, to admit several degrees of interaction and to keep the system open for extensions or adaptations of individual components to changing demands. Proofs and computations performed with Expander2 follow the rules and the semantics of swinging types.
(Peter Padawitz, Sebastian Venier, Karsten Lettow, Jochen Gerlach, Marcel Köppen, Markus Heller)